Intro to R - Ch 06.R

############################################################
# R script to accompany Intro to R for Business, Chapter 06#
# Written by Troy Adair                                    #
############################################################

## Going to be reading in a lot of data, so let's empty Environment
## and clean up Console
# Clean Up 
rm(list=ls(all=TRUE))
cat("\014") 

## Reading in external data
## Prior to attempting this section, download file
## "yellow-tripdata_2017-06.csv" from the link on intro-to-r.com
## and store it in the /Data subfolder for this project.
if (!require("here")) install.packages("here")
library("here")


# Also, edit the .gitignore file (if necessary) to exclude
# *.csv and *.RData files from being synced by Git. 
file.edit(".gitignore")

# Importing the file and measuring how long the import takes
### Run as a block of text to time #########
ptm <- proc.time()
DF <- read.csv(here("Data","yellow_tripdata_2017-06.csv"))
CSV_READ_TIME <- (proc.time() - ptm)
CSV_READ_TIME
############################################

# Looking at what we got
class(DF)
typeof(DF)
str(DF)


## Reading in our csv file using fread() from package data.table 
# Installing data.table (if required) and loading it into memory
if (!require("data.table")) install.packages("data.table")
library("data.table")

#Checking and setting number of cpu threads
getDTthreads()
getDTthreads(verbose=TRUE)
setDTthreads(0)
getDTthreads()

# Doing a timed read of the same file with fread()
### Run as a block of text to time #########
ptm <- proc.time()
DF <- fread(here("Data","yellow_tripdata_2017-06.csv"), header="auto", 
            data.table=FALSE)
FREAD_READ_TIME <- (proc.time() - ptm)
FREAD_READ_TIME
############################################

# Examining what we got
class(DF)
typeof(DF)
str(DF)
names(DF)

# Bringing in column headers as names and using them to set names
### Run as a block of text to time #########
ptm <- proc.time()
header <- read.table(here("Data","yellow_tripdata_2017-06.csv"), header = TRUE,
                     sep=",", nrow = 1)
DF <- fread(here("Data","yellow_tripdata_2017-06.csv"), skip=1, sep=",",
                  header=FALSE, data.table=FALSE)
setnames(DF, colnames(header))
rm(header)
FREAD_READ_TIME <- (proc.time() - ptm)
FREAD_READ_TIME
############################################

# Examining what we got again
class(DF)
typeof(DF)
str(DF)
names(DF)

# Examing the effects of multithreading
for(i in 1:getDTthreads()) {
  setDTthreads(i)
  print(getDTthreads())
  ptm <- proc.time()
  header <- read.table(here("Data","yellow_tripdata_2017-06.csv"), header = TRUE,
                       sep=",", nrow = 1)
  DF <- fread(here("Data","yellow_tripdata_2017-06.csv"), skip=1, sep=",",
              header=FALSE, data.table=FALSE,
              showProgress=FALSE)
  setnames(DF, colnames(header))
  rm(header)
  print(proc.time() - ptm)
  gc()
}

# But data.table is not the only game in town...
# What about package readr?

# Installing readr (if required) and loading it into memory
if (!require("readr")) install.packages("readr")
library("readr")

# A timed example of readr::read_csv()
### Run as a block of text to time #########
ptm <- proc.time()
DF <- read_csv(here("Data","yellow_tripdata_2017-06.csv"), col_names=TRUE)
READR_READ_TIME <- (proc.time() - ptm)
READR_READ_TIME
############################################

CSV_READ_TIME
FREAD_READ_TIME

class(DF)
typeof(DF)
str(DF)
names(DF)

# We've picked a winner: let's run with it. 
rm(list=ls(all=TRUE))
cat("\014")

header <- read.table(here("Data","yellow_tripdata_2017-06.csv"), header = TRUE,
                     sep=",", nrow = 1)
Yellow_Tripdata_2017_06 <- fread(here("Data","yellow_tripdata_2017-06.csv"),
                                 skip=1, sep=",",header=FALSE,
                                 data.table=FALSE)
setnames(Yellow_Tripdata_2017_06, colnames(header))
rm(header)

# Looking at our data
View(Yellow_Tripdata_2017_06)
str(Yellow_Tripdata_2017_06)

# Using head()
head(Yellow_Tripdata_2017_06)
head(Yellow_Tripdata_2017_06, n=3)
head(Yellow_Tripdata_2017_06$trip_distance, n=10)
head(Yellow_Tripdata_2017_06[4:5])

# Using summary()
summary(Yellow_Tripdata_2017_06)
summary(Yellow_Tripdata_2017_06 $ trip_distance)
#
# Throwing out "non-fares"
Yellow_Tripdata_2017_06 <- Yellow_Tripdata_2017_06[which(
  Yellow_Tripdata_2017_06$fare_amount>=0 & 
  Yellow_Tripdata_2017_06$fare_amount<100000),]
summary(Yellow_Tripdata_2017_06 $ fare_amount)

# Constraining passenger_count to = 1 or 2
Yellow_Tripdata_2017_06<-Yellow_Tripdata_2017_06[which(
  Yellow_Tripdata_2017_06$passenger_count==1 | 
  Yellow_Tripdata_2017_06$passenger_count==2),]
summary(Yellow_Tripdata_2017_06 $ passenger_count)

# Using data.table:fwrite()to save our curated data as csv:
fwrite(Yellow_Tripdata_2017_06,"Yellow_Curated.csv")

# Let's re-read our "original" data set,
# create a sample subset, and save it
# for the next chapter.

# First, clear memory and the Console 
rm(list=ls(all=TRUE))
cat("\014")

# Re-read the csv:
header <- read.table(here("Data","yellow_tripdata_2017-06.csv"), header = TRUE,
                     sep=",", nrow = 1)
DF <- fread(here("Data","yellow_tripdata_2017-06.csv"),
                                 skip=1, sep=",",header=FALSE,
                                 data.table=FALSE)
setnames(DF, colnames(header))
rm(header)

# Save the "bad" observations so we can clean them out
# in the next chapter
DF2<-DF[which(DF$total_amount<=0 |
                DF$fare_amount >=100000 |
                DF$fare_amount < 0 |
                DF$trip_distance >= 100),]
# Reform DF with only the "good" observations
DF<-DF[which(DF$total_amount >0 &
                DF$fare_amount <100000 &
                DF$fare_amount >= 0 &
                DF$trip_distance < 100),]

# Select a random subsample of 1,000,000 rows
set.seed(10)
index <- sample(1:nrow(DF), 1000000, replace=FALSE)

# Look at the index to see it's just row numbers
head(index)

# Copy the row numbers for the sample only into Yellow_Sample
Yellow_Sample <- DF[index,]

# Concatenate (or "bind") the random sample and the "bad" ones
Yellow_Sample <- rbind(DF2,Yellow_Sample)

# Save the data frame as an R data file
save(Yellow_Sample,file=here("Data","Yellow_Sample.RData"))